Editing Shader (section)

=== 3D shaders ===
3D shaders act on [[3D model]]s or other geometry but may also access the colors and textures used to draw the model or [[Polygon mesh|mesh]]. Vertex shaders are the oldest type of 3D shader, generally making modifications on a per-vertex basis. Newer geometry shaders can generate new vertices from within the shader. Tessellation shaders are the newest 3D shaders; they act on batches of vertices all at once to add detail—such as subdividing a model into smaller groups of triangles or other primitives at runtime, to improve things like [[curve]]s and [[:wikt:bump|bump]]s, or change other attributes.

==== Vertex shaders ====
Vertex shaders are run once for each 3D [[vertex (computer graphics)|vertex]] given to the graphics processor. The purpose is to transform each vertex's 3D position in virtual space to the 2D coordinate at which it appears on the screen (as well as a depth value for the Z-buffer).<ref>{{cite web|url=http://www.lighthouse3d.com/tutorials/glsl-tutorial/vertex-shader/|title=GLSL Tutorial – Vertex Shader|date=June 9, 2011}}</ref> Vertex shaders can manipulate properties such as position, color and texture coordinates, but cannot create new vertices. The output of the vertex shader goes to the next stage in the pipeline, which is either a geometry shader if present, or the [[rasterizer]]. Vertex shaders can enable powerful control over the details of position, movement, lighting, and color in any scene involving [[3D model]]s.

==== Geometry shaders ====
Geometry shaders were introduced in Direct3D 10 and OpenGL 3.2; formerly available in OpenGL 2.0+ with the use of extensions.<ref>[http://www.opengl.org/wiki/Geometry_Shader Geometry Shader - OpenGL]. Retrieved on December 21, 2011.</ref> This type of shader can generate new graphics [[primitive (geometry)|primitive]]s, such as points, lines, and triangles, from those primitives that were sent to the beginning of the [[graphics pipeline]].<ref>{{cite web|url=http://msdn.microsoft.com/en-us/library/bb205123(VS.85).aspx|title=Pipeline Stages (Direct3D 10) (Windows)|website=msdn.microsoft.com|date=January 6, 2021 }}</ref>

Geometry shader programs are executed after vertex shaders. They take as input a whole primitive, possibly with adjacency information. For example, when operating on triangles, the three vertices are the geometry shader's input. The shader can then emit zero or more primitives, which are rasterized and their fragments ultimately passed to a [[pixel shader]].

Typical uses of a geometry shader include point sprite generation, geometry [[Tessellation (computer graphics)|tessellation]], [[shadow volume]] extrusion, and single pass rendering to a [[cube map]]. A typical real-world example of the benefits of geometry shaders would be automatic mesh complexity modification. A series of line strips representing control points for a curve are passed to the geometry shader and depending on the complexity required the shader can automatically generate extra lines each of which provides a better approximation of a curve.

==== Tessellation shaders ====
As of OpenGL 4.0 and Direct3D 11, a new shader class called a tessellation shader has been added. It adds two new shader stages to the traditional model: tessellation control shaders (also known as hull shaders) and tessellation evaluation shaders (also known as Domain Shaders), which together allow for simpler meshes to be subdivided into finer meshes at run-time according to a mathematical function. The function can be related to a variety of variables, most notably the distance from the viewing camera to allow active [[level of detail (computer graphics)|level-of-detail]] scaling. This allows objects close to the camera to have fine detail, while further away ones can have more coarse meshes, yet seem comparable in quality. It also can drastically reduce required mesh bandwidth by allowing meshes to be refined once inside the shader units instead of downsampling very complex ones from memory. Some algorithms can upsample any arbitrary mesh, while others allow for "hinting" in meshes to dictate the most characteristic vertices and edges.

==== Primitive and Mesh shaders ====
Circa 2017, the [[AMD Vega]] [[microarchitecture]] added support for a new shader stage—primitive shaders—somewhat akin to compute shaders with access to the data necessary to process geometry.<ref>{{cite web|url=http://www.trustedreviews.com/news/amd-vega-specs-performance-release-date-technology-explained|title=Radeon RX Vega Revealed: AMD promises 4K gaming performance for $499 - Trusted Reviews|date=July 31, 2017}}</ref><ref>{{Cite web|url=https://techreport.com/review/31224/the-curtain-comes-up-on-amds-vega-architecture/|title=The curtain comes up on AMD's Vega architecture|date=January 5, 2017}}</ref>  

Nvidia introduced mesh and task shaders with its [[Turing (microarchitecture)|Turing microarchitecture]] in 2018 which are also modelled after compute shaders.<ref>{{cite web|url=https://devblogs.nvidia.com/nvidia-turing-architecture-in-depth/|title=NVIDIA Turing Architecture In-Depth|date=September 14, 2018}}</ref><ref>{{cite web|url=https://devblogs.nvidia.com/introduction-turing-mesh-shaders/|title=Introduction to Turing Mesh Shaders|date=September 17, 2018}}</ref> Nvidia Turing is the world's first GPU microarchitecture that supports mesh shading through DirectX 12 Ultimate API, several months before Ampere RTX 30 series was released.<ref>{{cite web | url=https://www.nvidia.com/en-us/geforce/news/directx-12-ultimate-game-ready-driver/ | title=DirectX 12 Ultimate Game Ready Driver Released; Also Includes Support for 9 New G-SYNC Compatible Gaming Monitors }}</ref>

In 2020, AMD and Nvidia released [[RDNA 2]] and [[Ampere (microarchitecture)|Ampere]] microarchitectures which both support mesh shading through [[DirectX#DirectX 12 Ultimate|DirectX 12 Ultimate]].<ref>{{Cite web|date=2020-03-19|title=Announcing DirectX 12 Ultimate|url=https://devblogs.microsoft.com/directx/announcing-directx-12-ultimate/|access-date=2021-05-25|website=DirectX Developer Blog|language=en-US}}</ref> These mesh shaders allow the GPU to handle more complex algorithms, offloading more work from the CPU to the GPU, and in algorithm intense rendering, increasing the frame rate of or number of triangles in a scene by an order of magnitude.<ref>{{Cite web|date=2021-05-21|title=Realistic Lighting in Justice with Mesh Shading|url=https://developer.nvidia.com/blog/realistic-lighting-in-justice-with-mesh-shading/|access-date=2021-05-25|website=NVIDIA Developer Blog|language=en-US}}</ref> Intel announced that Intel Arc Alchemist GPUs shipping in Q1 2022 will support mesh shaders.<ref>{{Cite web|url=https://www.anandtech.com/show/16895/a-sneak-peek-at-intels-xe-hpg-gpu-architecture|title=Intel Architecture Day 2021: A Sneak Peek At The Xe-HPG GPU Architecture|first=Ryan|last=Smith|website=www.anandtech.com}}</ref>